US Orbital Segment in the context of "European Space Agency"

The International Space Station (ISS) is a large space station that was assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United States), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada). As the largest space station ever constructed, it primarily serves as a platform for conducting scientific experiments in microgravity and studying the space environment.

The station is divided into two main sections: the Russian Orbital Segment (ROS), developed by Roscosmos, and the US Orbital Segment (USOS), built by NASA, ESA, JAXA, and CSA. A striking feature of the ISS is the Integrated Truss Structure, which connect the station's vast system of solar panels and radiators to its pressurized modules. These modules support diverse functions, including scientific research, crew habitation, storage, spacecraft control, and airlock operations. The ISS has eight docking and berthing ports for visiting spacecraft. The station orbits the Earth at an average altitude of 400 kilometres (250 miles) and circles the Earth in roughly 93 minutes, completing 15.5 orbits per day.

Unity, also known as Node 1, is the first U.S.-built component of the International Space Station (ISS). This cylindrical module, constructed of steel by Boeing for NASA, serves as the critical link between the orbiting laboratory's Russian Orbital Segment and US Orbital Segment.

Unity was launched on December 4, 1998, aboard the Space Shuttle Endeavour on STS-88. Two days later it was berthed to the previously launched Zarya module, marking the first connection between ISS components. Its six Common Berthing Mechanism (CBM) locations (forward, aft, port, starboard, zenith, and nadir) facilitate connections to other modules. At launch, two CBM locations were fitted with Pressurized Mating Adapters (PMA), one of which enabled the mating with Zarya.

Zvezda, also known as the Zvezda Service Module, is a module of the International Space Station (ISS). It was the third module launched to the station, and provided all of the station's life support systems, some of which are supplemented in the US Orbital Segment (USOS), as well as living quarters for two crew members. It is the structural and functional center of the Russian Orbital Segment (ROS), which is the Russian part of the ISS. Crew assemble here to deal with emergencies on the station.

The module was manufactured in the USSR by Energia, with major sub-contracting work by GKNPTs Khrunichev. Zvezda was launched on a Proton launch vehicle on 12 July 2000, and docked with the Zarya module on 26 July 2000 at 01:45 UTC. It is a descendant of the Salyut programme's.

The Common Berthing Mechanism (CBM) connects habitable elements in the US Orbital Segment (USOS) of the International Space Station (ISS). The CBM has two distinct sides that, once mated, form a cylindrical vestibule between modules. The vestibule is about 16 inches (0.4 m) long and 6 feet (1.8 m) across. At least one end of the vestibule is often limited in diameter by a smaller bulkhead penetration.

The elements are maneuvered to the berthing-ready position by a Remote Manipulator System (RMS). Latches and bolts on the active CBM (ACBM) side pull fittings and floating nuts on the passive CBM (PCBM) side to align and join the two.

A Pressurized Mating Adapter (PMA) is a component used on the International Space Station (ISS) to convert the Common Berthing Mechanism (CBM) interface used to connect ISS modules to an APAS-95 spacecraft docking port. Three PMAs are attached to the US Orbital Segment of ISS. PMA-1 and PMA-2 were launched along with the Unity module in 1998 aboard STS-88; PMA-3 was launched in 2000 aboard STS-92. PMA-1 permanently connects the Unity and Zarya modules. International Docking Adapters were permanently installed on PMA-2 and PMA-3 in 2017 to convert them from the APAS-95 standard to the newer International Docking System Standard (IDSS).